1. Field of the Invention
This invention relates generally to a load lock adjustment mechanism for securing freight inside a trailer and, more particularly, the invention relates to a load lock adjustment mechanism enabling the load lock to adjust to different trailer widths.
2. Description of the Prior Art
The prior art load lock 10, as illustrated in FIG. 1, has two lengths of round tubing 12, 14 with the tube 12 telescopingly received within the tube 14. A gear rack and pinion system 16 is used to adjust the position of one of the tubes with respect to the other tube. The gear rack and pinion system 16 includes a rack 18 secured at one end 18a to the tube 12 (or the tube 14) and extends in the direction of and over the other tube 14. A handle-locking device 20 is attached to the tube 14 (not the tube to which the rack is attached). The handle-locking device 20 has a U-shaped plate 22, which is disposed about the tube 14. The distance between the two free ends 22a, 22b (not shown) is wide enough to receive the rack 18. A bolt 24 secured between the two free ends 22a, 22b forms the center pin extending through a pinion gear 26. The pinion gear 26 can rotate about the center pin 24 extending through a hole 25. A handle 28 is secured to the pinion gear 26. The pinion gear 26 has a section without gears, preferably disposed in the opposite the direction to which the handle extends, so that when the handle is positioned perpendicular to the centerline 30 through the telescoping tubes 12, 14, the tubes can move with respect to each other. When the handle 28 is pivoted to a positioned parallel to the centerline 30, the pinion gear 26 engages the rack 18 and moves the telescoping tubes 12, 14 in opposite directions from each other. The handle 28 can be locked in place by conventional means.
Pads 32 and 34, formed of a slightly compressible material such as rubber, each have connecting rod 36 and 38, respectively, extending there from. The connecting rods 36 and 38 are attached to tubes 12 and 14, respectively, by bolts 40 and 42, respectively, extending through holes 41, 43 (see FIG. 3) in the tubes 12 and 14 and therefore have some degree of movement with respect to the tubes.
To install the conventional load lock 10 in the semi-trailer, the handle lock 28 is released and moved to a position parallel to and above the tube 12. Next, while holding the load lock with the pad 34 at the end of the larger diameter tube 14 against the semi-trailer wall and in a parallel position to the trailer floor, the smaller diameter tube 12 is extended until the pad 32 at the end of that tube touches the opposing wall. Then the handle 28 is moved 180 degrees from the position above the tube 12 in position above the tube 14 whereby the pinion gear 26 moves the rack 18 to further push the tubes 12, 14 away from each other to generate a clamping force that presses the pads 32, 34 into securing engagement with the side walls of a semi-trailer. The handle locks into place securing the load lock 10 between the trailer walls. The load lock 10 is supposed to secure the freight inside the semi-trailer in its loaded positioned until it is unloaded at the customer's facility.
The problem with the load lock 10 is that it is unable to be adjusted to the different widths encountered from trailer to trailer to a sufficient degree that the maximum clamping force is exerted against the trailer sidewalls. The reason for this inability to properly adjust the length of the load lock is caused by the coarse pitch of the rack and pinion 16. The pitch has to be coarse to make the rack strong enough to withstand the force exerted in order to hold the load lock in place while in transit. When the load lock is extended and the handle clamping maneuver results in the pinion hitting a tooth on the rack, the load lock length has to be slightly shortened to allow the pinion to engage between the teeth on the rack. This result in less clamping pressure than is needed to keep the load lock in place between the walls of the trailer. The reduced clamping pressure sometimes results in the load lock falling to the floor of the trailer. This can result in the freight shifting and causing damage to the freight. Sometimes, when the load lock falls to the floor, the driver is injured by falling freight while in the process of preparing the trailer to be unloaded at the customer's facility.